Pneumatic follow-up system



INVENTOR.

PAUL F. K. ERBGUTH June 1958 P. F. K. ERBGUTH PNEUMATIC FOLLOW-UP SYSTEM Filed Marbh s, 1955 United. States Patent 2,838,028 7 PNEUMATIC FOLLOW-UP SYSTEM Paul F. K. Erbguth, Great Neck, N. Y., assignor, by mesne assignments, to Dnystrom, Incorporated, Murray Hill, N. J.,'a corporation of New Jersey Application March 8, 1955, Serial No. 492,930

6 Claims. (Cl. 121---41) This invention relates to pneumatic systems and more particularly to such comprising a vane carried by the rotatable pointer and movable between a nozzle from which low pressure air flows and a coaxially-disposed nozzle receiving air from the first-mentioned nozzle, except when cut off by the vane, including a coupling rotatable coaxially with the pointer and on which the nozzles are mounted, with relay means to cause the rotatable coupling to follow movement of the said pointer.

Pneumatic systems of the class contemplated by this invention comprise a device or mechanism for sensing changes in a variable condition, examples being electrical measuring instruments with pointers indicating current or voltage, and devices with parts like pointers rotatable in response to changes in weight, humidity, etc. Such devices may be associated with pneumatic relays or couples comprising a discharge nozzle from which an elastic fluid flows under low pressure and a cooperating receiving nozzle aligned with the discharge nozzle to receive elastic fluid therefrom except as cut off by a vane carried by the sensing mechanism.

The present application is directed to a system in which the cooperating nozzles are mounted on a coupling rotatable coaxially with the pointer or other lever, and relay means are provided for causing said coupling to rotate so as to follow rotation of the said pointer or other lever carrying the vane.

An object of this invention is the provision of a pneumatic system in which a vane normally is disposed in an air stream flowing between two nozzles and including a coupling rotatable coaxially with a lever carrying the vane and carrying the nozzles, and means effective upon movement of the vane to effect a corresponding rotation of the coupling thereby to maintain the vane in a throttling position in the air stream.

An object of this invention is the provision of a pneumatic couple in which axially-aligned nozzles are mounted on a coupling rotatable coaxially with a lever, said lever being responsive to changes in a variable condition.

An object of this invention is the provision of a pneumatic system comprising a vane carried by a rotatable lever responsive to changes in a variable condition, axiallyaligned nozzles carried by a coupling rotatable coaxially' with the lever, means maintaining an air stream across the nozzles except as cut off by the vane, air-operated means responsive to changes in air pressure in one of the nozzles brought out by a change of vane position in the air stream, and mechanism operated by said air-operable means to eifect a rotation of the coupling in a sense to maintain the vane in a throttling position in the air stream.

An object of this invention is the provision of an electropneumatic system comprising an electrical instrument having a rotatable pointer carrying a vane, a pair of axiallyaligned nozzles disposed on opposite sides of the vane, a rotatable coupling, means maintaining an air stream across the nozzles except as inhibited by the vane, an air relay responsive .to changes in the air pressure in one of the nozzles as brought about by movement of the vane in the air stream, and mechanism actuated by the air relay to rotate the said coupling to thereby maintain the vane in a throttling position in the air stream.

These and other objects and advantages of the invention will become apparent from the following description when taken with the accompanying drawings. It will be understood, however, that the drawings are for purposes of illustration and are not to be construed as defining the scope or spirit of the invention, reference being had for the latter purpose to the claims appended hereto.

In the drawings wherein like reference characters denote like parts in the several views:

Figure 1 is a diagrammatic representation of an electropneumatic follow-up system made in accordance with this invention;

Figure 2 is a perspective view of the rotatable coupling carrying the aligned nozzles;

Figure 3 is a fragmentary sectional view taken along the line III-III of Figure 2 and drawn to an enlarged scale; and

Figure 4 is a fragmentary view showing the normal position of thevane substantially in the center of the air stream flowing between the aligned nozzles.

Reference is now made to Figure l which illustrates an electro-pneumatic follow-up system. Here the conditionsensing device is an electrical instrument, such as a millivoltmeter, having a vane 21 secured to the pointer 22. The instrument may be of conventional construction having a wire wound movable coil 24, rotatable on pivots 25, 26 between the poles of a permanent magnet, not shown. Each of the pivots has secured thereto a spiral hair spring, 27, 28, which hold the coil in a given zero position until an electric current flows through the coil. Such current may be generated by a thermocuple 29 serving as a temperature-sensing element in a furnace, not shown. The instrument may include a scale 30 calibrated in suitable values as, for example, temperature.

The vane 21 is movable, upon rotation of the pointer, between a pair of axially-aligned, spaced nozzles 31, 32. These nozzles form a pneumatic couple and are carried by a hollow coupling 33 mounted for coaxial rotation with the pointer by the pivots 34, 35. A spring 36 has one end fastened to the pivot 35 and the other end to a fixed member 38, said spring being arranged to bias the couple in a counter-clockwise rotation, that is, toward the zero position of the pointer relative to the scale 30. A wire 65 is entwined around the coupling and has one end secured to the coupling and the other end to an arm 64 secured to the shaft 59.

Air is fed to the coupling 33 by means of a tube 39, the pressure of the air transmitted thereto being reduced as by passing through a flow restrictor 41. Air is supplied to the tube 42 feeding the discharge nozzle 31 from the right hand hollow interior of the coupling 33. Air is supplied to the left hand hollow interior of the coupling 33, which is, of course, separated from the right hand hollow interior or cavity, by means of tube 43. From the interior cavity at the left hand end, air passes through tube 44 to air relay 45. The structural details of the coupling will be described hereinbelow with reference to Figures 2 and 3.

The air relay 45 comprises a chamber closed by a diaphragm 46 connected to a lever 47 that is pivoted to the relay housing as indicated at 48. At its other end the lever carries a flapper 49, normally disposed adjacent to nozzle 51 from which air flows. The nozzle 51 is supplied with air under pressure, through a tube 52, which may, if desired, also contain-a flow restric'tor 53. In general, the air pressure within the tube 52 is of the order of pounds per square inch. On the other hand, the pressure of the air in the tube 42 is very low in the range of less than 3 inches of water thereby eliminating Patented June 10, 1558 adverse reaction between the vane and the air stream flowing between the discharge nozzle 31 and the receiving nozzle 32. When the pressure in the tube 44 decreases, due to the vane passing farther into the air stream betweenthe nozzles 31 and 332, the diaphragm as moves downwardly, moving the flapper 4'9 closer to the nozzie 51, and correspondingly effecting an increase in pressure in the tube 52 and the bellows assembly 54, connected thereto by the tube 55*. it will be understood that in practice the leading or upscale edge of the vane normally is disposed in the air stream and it is the movement' of this vane edge substantially in the center of the air streamwhichinhibits more or less the flow of air from the discharge nozzle to the receiving nozzle.

Upon such increase in air pressure, the bellows 54 is compressed. A rod 57 has its lower end secured to the bottom of the bellows and its upper end pivotally-connected' at 58 to a crank 56' that is secured to the shaft 55. Consequently, a compression of the bellows results in a counter-clockwise rotation of the shaft and a clockwise rotation of the coupling 33 by means of the arm 64' and the wire 65. It will be apparent, then, that an upscale movement of the pointer, resulting in a movement of the vane further into the air stream results in a corresponding rotation of the coupling 33 until the vane again occupies substantially its initial, or throttling, position in the air stream. In order to prevent movement of the vane 21 beyond the air stream upon upscale deflection of the pointer a suitable stop 55 is secured to the nozzle 32. The shaft 59 may also operate an arm 63 carrying a pen cooperating with a movable chart to form a record'er. Obviously, such record will correspond to the position of the instrument pointer, or the instantaneous state of the variable condition under consideration.

Referring now to Figures 2 and 3 for preferred details of the rotatable coupling 33 and the parts associated therewith, it will be seen that this coupling, here designated 33a, is provided with a hollow cavity or pocket 66, at each end. The right-hand pocket, as viewed in Figure 3, has a port 67 communicating with a tube 42, which tube. is connected to the discharge nozzle 31. The lefthand cavity 66 has a similar port communicating with the tube 43, on the free end of which is mounted a receiving nozzle 32.

The coupling 33a is mounted between. standards or columns 65 and 69, upstanding from base portions 71 and 72 forming a base. The upper portion of these columns 68 and 69 are respectively provided with air receiving and dispensing cavities 73. The receiving cavity 73 in thecolumn 63 has air fed thereto by means of tube 3% containing a restriction 43a therein, so as to reduce the air pressure to one of about one inch of water and not more than three inches of water. From this receiving cavity73, air passes to the adjacent cavity 66 in the coupling 33a through a hollow shaft or pivot 74 on which the coupling rotates. The outer end of the hollow shaft 74 is fixed in the column 63 and carries a spacer or washer member 75 which is engageablc by the adjacent outer plate 76 of the coupling 33a to prevent the attaching screws 77 from rubbing on the column 6%. Leakage of air between the hollow shaft 74 and the coupling 33a is prevented by a metal bearing member 78 held in place by the plate 76, with a resilient mc-rnbrane 79 secured between the bearing member and shaft. The membrane 79 tightly encircles the shaft 74 and provides a sealing action, while not appreciably interfering with the required rotation of the coupling about the shaft.

The cavity at the other end of the coupling 33a is like the described cavity 73 illustrated in Figure 3, except that air is fed thereto through the nozzle 32 and the tube as, except when cut off by the vane 21. From this cavity, air then feeds through a similar hollow shaft, similarly sealed, to a similar cavity in the column 69, and from there out through pipe 44 to a relay which 4 i may be like that designated 45 in Figure 1. The hollow coupling 33ahas the wire 65 connected to a point at its circumference designated 81, so as to provide for followup action of said coupling and associated nozzles, as has been described with reference to Figure 1. However, in the present instance, instead of having a spiral hair spring 36, to retain the wire 65 under tension, there is a coil spring 36a connected between a fixed abutment 37 and a resilient wire $2, the latter being attached to a surface of the coupling.

From the foregoing disclosure it will be seen that I have provided an electro-pneumatic system responsive to changes in a variable condition as, for example, temperature. The system is self-balancing in that any displacement of the vane results in a corresponding follow-up rotation of the aligned nozzles to thereby return the system to balance. Since the position of the rotatable coupling carrying the aligned nozzles will always correspond to the position of the instrument pointer, the actual deflection of the instrument can be recorded in a recorder by a pen actuated as by the arm 63, Figure l, movable in accordance with rotation of the rebalancing shaft 59. Also, since the variation in air pressure effective to move the bellows assembly 54 varies in accordance with the position of the instrument pointer suitable, remotely-positioned indicating and/or control apparatus can be actuated by connecting same to the tube 55.

While I have described a specific electro-pneumatic system, it will be apparent that my pneumatic follow-up arrangement is not restricted for use with a conditionsensing device of electrical character. Any rotatable pointer, or lever, system may be utilized to move th vane in the air stream.

Having now described my invention in detail in accordance with the requirements of the Patent Statutes. various changes and modifications will suggest themselves to those skilled in the art, and it is intended that such changes and modifications shall fall within the scope and spirit of the invention as recited in the following claims.

I claim:

1. A pneumatic follow-up system comprising a vane movable by a rotatable member in response to changes in a variable condition, a pair of axially-aligned nozzles disposed on opposite sides of the vane and carried by a coupling member rotatable coaxially with the said rotatable member, means normally maintaining an air stream between the nozzles, air-operated means responsive to changes in the air pressure within one of the nozzles as brought about by movement of the vane in the air stream, and mechanism responsive to the said air-operated means to rotate the coupling member in a direction to maintain the vane in a predetermined throttling position in the air stream.

2. A pneumatic follow-up system comprising a vane movable by a rotatable member in response to changes in a variable condition, a pair of axially-aligned nozzles disposed on opposite sides of the vane and carried by a coupling member rotatable coaxially with the rotatable member, a source of low pressure air connected to one of the nozzles, an air relay having a chamber closed by a diaphragm and connected to the other nozzle, means actuated by the diaphragm to correspondingly vary the pressure in an air line, a bellows responsive to changes in the pressure in the air line and means rotating the coupling member in accordance with the movement of the bellows.

3. The invention as recited in claim 2, wherein the means rotating the coupling member comprises a rotatable shaft, means biasing the shaft for rotation in one direction. a connecting link between the shaft and the bellows, and a flexible filament having one end entwined about the coupling member and secured thereto and the other end secured to an arm carried by the said shaft.

4. 'An electro-pneumatic system comprising an electrical instrument having apointer carrying a vane, a pair I chamber closed by a diaphragm and connected to the other nozzle, means actuated by the diaphragm to correspondingly vary the pressure in an air line, a bellows movable in accordance with the pressure variations in the air line, and a mechanical linkage mechanism coupled between the bellows and the coupling member and effective to rotate the coupling in accordance with movement of the bellows.

5. The invention as recited in claim 4, wherein the said coupling member comprises a cylindrical member having axial bores in each end, radial ports communicating with each bore, tubes carrying the aligned nozzles and inserted in each port, axially-aligned hollow shafts each shaft having an end disposed Within one of the said bores and the opposite end communicating with hollow pockets formed in spaced standards which serve as a support for the coupling member, and air-sealing means disposed between each shaft and the cylindrical member.

6. The invention as recited in claim 5, wherein the mechanical linkage mechanism comprises a rotatable shaft connected by a crank to the said bellows, and a flexible filament having one end secure-d to the coupling member .and the other end secured to an arm rotatable with the said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 1,851,723 Neidow Mar. 29, 1932 2,058,642 Sperry Oct. 27, 1936 2,228,022 Ziebolz Ian. 7, 1941 2,254,098 Ziebolz Aug. 26, 1941 2,276,221 Magnesen Mar. 10, 1942 2,455,539 Wahl Dec. 7, 1948 2,568,092 Sloan Sept. 18, 1951 FOREIGN PATENTS 390,550 Germany Feb. 20, 1924 

